Re: [Xen-devel] [PATCH] xen/memguard: Drop memguard_init() entirely

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 19/02/16 14:44, Jan Beulich wrote:
>>>> On 18.02.16 at 19:03, <andrew.cooper3@xxxxxxxxxx> wrote:
>> It is not obvious what this code is doing.  Most of it dates from 2007/2008,
>> and there have been substantial changes in Xen's memory handling since then.
> Deleting code which isn't understood what it is or was once used
> for is sub-optimal.
>
>> It was previously optional, and isn't needed for any of the memguard
>> infrastructure to function.  The use of MAP_SMALL_PAGES causes needless
>> shattering of superpages.
> Perhaps that's what is its purpose? Let's ask Keir, whom you didn't
> even Cc.

I don't see this patch being different in nature to your "x86: drop
failsafe callback invocation from assembly".

As I explain in the second paragraph, these calls are strictly optional,
as they are omitted for release builds.  They also have no impact on the
rest of the memguard infrastructure to function, as
__memguard_change_range() also uses map_pages_to_xen().

So despite not being sure why it is like it is, I am stating with that
it is not needed with Xen in its current form.

~Andrew

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